Tube drawing nib mount



l Patented Nov. 1940 Edgar W.y Engle, Noi-oton, and Hershel'Bryan Appuuonnmber l16, 1937, serial No. 130,073

The present invention relates to means for mounting the nibs thereof. The nibs are formed from hard metallic materials. such I as cemented hard metal carbides, having 'low tensile strength, great hardness, highA compres-r sive strength and resistance to abrasion, and low coeilicientl of thermal expansion. Examplesv f such materials are described and claimed inl the Schroter Patent No. 1,549,615, issued August 11, 1925, whichconsist of minutev particlesv of extremely f .hard tungstencarbide cemented together with a small amount of cobalt. Heretofore sucha nib in the shape of a sleeve was secured lto a steel shank by means'of afsteel stud extending through'and snugly fitting within the nib sleeve. VDiiliculty was experienced in that during use the nib sleeve frequently was cracked orfits surface was spalled,` now believed la to have been caused by the pressure'exerted on the nib' sleeve by the greater expansion of the stud when heat was developed during the drawing vf. `A general objectof the present invention is 25 the provision ofemcientand simple means for permitting the nib vfsleeve-su'pporting stud to eitpand without exerting undue pressure on the nibsleeve. `1

yMore specific and furthei` objects are the pro- N vision oa-tube drawing mandrel, and a shank and nib sleeve-supporting'stud, characterized by a recess or recesses" in the nib sleeve support which eiectively permits expansion of the klatter without exerting undue pressure on'the nib 8l sleeve; to provide, if desired, in the recesses in the nib` sleeve support a mass or massesof 'soft metallic material for cushioning such' expansion; andthe provision of structural embodiments of the device -'which arereadily constructed' and allow'eiiicient use and'operation thereof.'

Other objects of be obvious and will in part appear hereinafter.

The invention accordingly comprises 'the fea` tures of'construction, combination offelements, and arrangementfof parts; which will be exemplied in the construction hereinafter set.

forth, and the scope of theinvention will beindicated in the claims.

For a fuller understanding of the nature'and' objects ofthe invention reference should be had connection with the accompanying drawing, in

which: f Fig. 1 is a side elevational view witnparts Q5 broken away Vand in section ofa mandrel of the kthe invention will vin. partl to the following detailed description taken in] tube draw. ing mandrels and, more particularly, to the present invention associated` with a suitable drawing die;l Fig. 2 is an enlarged `side elevationiv.l view with parts broken l away `and'in section'of a modified structure of the mandrel .of thefpresent invention; and f Q Fig. `3 is ya greatly enlarged detailed view in section of a portion of the nib and thesupport shown in Fig. 2, showing the probable operation thereofv during use Ain permitting expansion of expansion vof `'the' stud from exerting undue pressurejon the surrounding nib, the material of which has a much lower coeicient of thermal expansion ,than the vstud material, it" has found that spalli'rig of the'surface of thelatter 'and breakage islargely" eliminated. f

With the elimination of the apparentlyunnecessary requirement ofa highdegree of mechanical supportfior the nibby the stud'itis now possible to use a more'elastic and tougher' metallicmaterial 'for' the shank'and stud and I the use 'of shanks and studs of Vsmaller diameters than. heretofore used with ynibs of given diameters. This has been found to permit 'use 10 the support vwithout exerting undue pressure on of` stronger nibs and largely toeliminate breakage ofI Shanks andstuds. Highly elastic steelof;

great strength, such as S. `A. E. 3250 having a i Rockwell C hardness of from about 40 to 50 has been 'found to be desirable materialfor shanks and studs." A' suitable material for the nib mayv kbecexn'ented tungsten carbide containing about y L It is to be understood, how-' ever, that the 'invention is not limited vto the 6%r to 16% cobalt.v

useofthese specic materials. y

vIn the drawing 'are shown man 'drels ofthe present invention which are suitable for use; in drawing tubes. Thevsteel mandrel shank'ltjis secured to a supporting rod y(not shown) in any suitame way'suenby the threaded secret u shown 'in dottedglines'.v 'I'he other end of the mandrel'shanki0 -is'reduced in diameter to'` form a stucly i2` on ywhich is seatedy a nib sleeve I3*v held in position by a collar i4 threadedfupo'n the outer end of the stud as shown. A suitable drawing die I5 surrounds the nib I3 which is preferably slightly tapered. A tube to be reduced in diameter is drawn toward the free end of the mandrel between the drawing die I5 and the nib I3. Similar devices may be used to smooth out excess weld materials on the outer and/or inner surfaces of welded tubes, -or for changing the diameter of the tube passage or thickness of the wall or both.

In accordance with the present invention expansion of the stud I2 due to heat developed during the drawing of the tubes may be prevented from exerting undue pressure on the nib by splitting the stud I2 longitudinally with a milling cutter to provide a slot I6. The slot I6 preferably extends beyond the inner end of the seat for the nib sleeve provided by the stud I2 as shown. The slot I6 is preferably filled with a mass I1 of soft metallic material, such as, vfor example, copper, brass, bronze, solder or brazing material, which cushions the radial expansion of the stud I2. `The stud I2 may additionally be provided, if desired, with asimilar slot arranged at a radial angle of say 90 to the slot I6. Any number of such slots arranged as desired obviously may be used.

Any suitable means of providing a plurality of lands and intervening depressions in the nib sleeve-seating surface of the stud with, if desired, the depressions partly or wholly'lled with soft metallic material, may be used as alternative cushioning means. For example,` one or more longitudinally or transversely extending grooves or slots may be formed in the niby sleeve-seating surface of the stud, filled if desired with soft metallic material. 'I'he stud may be formed separately from the shank and secured thereto in any suitable manner. If the studis formed separately from the shank, it can more readily be heat-treated to obtain desired physical properties, such as a highdegree of elasticity. The end of the stud may be received and pinned or threaded into a socket in the end of the shank Ill. In Fig. 2 such a structure is shown by way of example. The stud is provided with a head i8 and a shankl I9 threaded throughout its entire length as shown. 'I'he threads 2li-20, preferably having rounded or flattened tops, constitute elastically supporting or seating lands for the nib sleeve I3 and a groove or grooves 2I-2I between the lands 2li- 20 adapted to lie beneath the nib sleeve may be filled with a mass or masses 22-22 of soft metallic material. k

In accordance with the present invention the nib sleeve is held in position by a snugly fitting seat, chattering thereof is avoided, and the expansion of the steel supporting stud'due to heat developed during tube drawing is prevented from exerting undue pressure upon the nib sleeve. For example, when a threaded stud such as that shown in Fig, 2,is used which has been properly heat-treated to develop a certain elasticity, the expansion vof the steel against the inner surface of the nib will cause the sides of the threads 20-20 to distort or bulge into grooves ZI-ZI, as shown in Fig. 3, without exceeding the elastic limit of the steel. If the grooves 2I-2I are filled with masses 22-22 of soft metallic material these will cushion the expansion of the steel. Obviously the use of masses 22-22 of soft metallic material are not essential to the practice of the invention, the elastic steel itself cushioning the nib which is held snugly in position free from chattering by the lands provided by the threads ZIJ-20, and the grooves 2I-2I permitting distortion of the sides of the threads during expanson to relieve the nib sleeve from the enornius forces that may be developed by the expansion of a tightly fitting solid stud.

, Since certain changes may be made in the above construction and different embodiments of the invention could be made without departing from the scope thereof, it is intended that all lmatter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all of the generic and specic features of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

Having described our invention, what we claimas new and desire to secure by Letter Patent is: 4

1. Means for securing a hard metallic nib sleeve to the shank of a tube drawing mandrel, said means comprising a resilient metallic stud having a recess therein to permit radial expansion without exerting undue pressure on the nib.

2. Means for securing a hard metallic nib sleeve to the shank of atube drawing mandrel,

said means comprising a resilient metallic stud having a plurality of vlands and intervening de. pressions on the nib sleeve-seating surface there.l of to permit radial expansion without exerting undue pressure on the nib. y

3. Means for securing a hard metallic nib sleeve having a smooth inner surface tothe shank of a tube drawing mandrel, said means comprising a resilient metallic stud having the nib sleeve-seating surface thereof grooved to form elastically supporting-lands, said grooved surface extending the full working length of said sleeve.

4. Means for securing a hard metallic nib sleeve to the shank of a tube drawing mandrel, said means comprising a resilient metallic stud having spirally arranged nib sleeve-seating lands and intervening grooves on the surface thereof, said lands and grooves extending the lfull working length of said sleeve.

5. Means for securing a hard metallic nib sleeve to the shank of a tube drawing mandrel, comprising a metallic stud having soft metallic Inaterial located in a recess therein to cushion radial expansion.

6. Means for securing a hard metallic nib sleeve to the shank of a tube drawingmandrel, com*- prising a metallic stud having a slot extending longitudinally thereof and soft metallic material located in the slot to cushion radial expansion.

7. Means for securing a hard metallic nib sleeve to the shank of a vtube drawing mandrel, comprising a metallic studhaving a plurality of lands and intervening depressions on the nib-sleeveseating surface thereof and soft metallic material in the depressions to cushion radial expansion.

8. Means for securing a hard metallic nib sleeve to the shank of a tube drawing mandrel, comprising a metallic stud having the shank thereof threaded and the grooves adapted to lie beneath the nib sleeve filled with soft metallic material to cushion radial expansion.

9. A mandrel shank having. an end thereof reduced to form a nib sleeve supporting stud, said stud being split longitudinally to form a slot, and a mass of soft metallic material Ain the. slot to cushion radial expansion.

l0. A tube drawing mandrel comprising a metallic shank, a hard metallic nib sleeve, a metallic stud snugly itting within said sleeve and mounted on an end of said shank to secure said nib sleeve coaxially to said shank, the material of said stud having a higher coemcientof thermal expansion than the material oi said nib,rand a mass of soft metallic material located in a recess in said stud to permit radial expansion thereof without exerting undue pressure on said nib.

11. A tube drawing mandrel comprising a steel shank, a cemented hard metal carbide nib sleeve, a steel stud snugly fitting within said [nib sleeve and mounted on an end of said shank to secure said nib sleeve coaxially tosaid shank, said stud having a plurality of nib sleeve-seating lands and intervening depressions topermit radial expansion of the stud without exerting undue pressure 0n the nib.

n 12. A tube drawing mandrel a shank and a resilient metal stud, a hard metallic nib" sleeve tted snugly onto. saidr stud, saidsleeve having a straight, cylindrical hole therethrough of uniform diameter and a smooth interior surface, means for securing said sleeve in position 5 on said stud, and means permitting radial expansion of said stud withoutvexert'ing undue pressure on said sleeve. 'v n v v 13. A tube drawing mandrel comprising a shank 10 and a resilient metal stud, a hard metallic nib sleeve tted snugly ontoysaidstud, said sleeve having a smooth interior surface, means for securing said sleeve in position on said stud, and a recess in the portion oi' said stud within said 15 sleeve, said recess permitting radial expansion of ysaid stud without exerting undue pressure lon said sleeve. l

EDGAR W. ENGLE. l 1

kBRYAN DUNCAN: 20 

